In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drive train, but must do so while maintaining reasonable levels of performance, range, reliability, safety and cost.
In recent years there have been several incidents of a rechargeable battery pack, contained within a laptop computer or utilized in a vehicle, catching on fire. As a result, one of the primary issues impacting consumer confidence with respect to both hybrid and all-electric vehicles is the risk of a battery pack fire.
Rechargeable batteries tend to be relatively unstable and prone to thermal runaway, an event that occurs when a battery's internal reaction rate increases to such an extent that it is generating more heat than can be withdrawn. Thermal runaway may be the result of a battery short, a manufacturing defect, improper cell use, or damage such as that which may be sustained during an accident or when road debris dents or punctures the battery pack. If the reaction rate and the generation of heat go unabated during the thermal runaway event, eventually the generated heat becomes great enough to cause the battery and materials in proximity to the battery to combust. Therefore when the battery undergoing thermal runaway is located within a battery pack containing tens or hundreds of batteries, a single event can quickly propagate throughout the pack, dramatically increasing the likelihood of property damage as well as the risk to people in close proximity to the vehicle.
Vehicle manufacturers have employed a variety of techniques to both minimize the risk of a battery undergoing thermal runaway and control the propagation of the event if one should occur. These techniques include ballistic shields to prevent battery pack damage from road debris, monitors that detect battery malfunctions, monitors that detect the onset of a thermal runaway event, and advanced thermal management and fire control systems that help to limit event propagation. While these techniques may reduce the likelihood of a thermal runaway event and limit its effects when one does occur, until improvements in batteries and battery chemistries completely eliminate such events, additional systems are required that can be used to further minimize the risk to people and property alike. The present invention provides such a system.